This invention relates to a scroll-type positive fluid displacement apparatus and more particularly to a scroll-type apparatus having a fully compliant, i.e. axially and radially compliant, floating scroll mechanism.
There is known in the art a class of devices generally referred to as xe2x80x9cscrollxe2x80x9d pumps, compressors and expanders, wherein two interfitting spiroidal or involute spiral elements are conjugate to each other and are mounted on separate end plates forming what may be termed as fixed and orbiting scrolls. These elements are interfitted to form line contacts between spiral elements.
A pair of line contacts and the surfaces of end plates form at least one sealed off pocket. When one scroll, i.e. the orbiting scroll, makes relative orbiting motion, i.e. circular translation, with respect to the other, the line contacts on the spiral walls move along the walls and thus changes the volume of the sealed off pocket. The volume change of the pocket will expand or compress the fluid in the pocket, depending on the direction of the orbiting motion.
An early patent to Creux (U.S. Pat. No. 801,182) describes this general type of device. Subsequent patents which have disclosed scroll compressors, expanders and vacuum pumps are: U.S. Pat. Nos. 6,123,529, 6,068,459, 5,961,297, 5,855,473, 5,788,470, 5,775,893, 5,755,564, 5,690,480, 5,632,611, 5,624,247, 5,616,015, 5,556,269, 5,322,426, 5,304,047, 5,247,795, 5,171,140, 5,098,265, 4,731,000, 4,677,949, 4,558,997, 3,989,422, 3,802,809, 3,600,114, 3,560,119, 3,011,694, 2,494,100, 2,475,247, 1,041,721. These prior patents provide so-called xe2x80x9cdual scrollxe2x80x9d structure, i.e. the orbiting scroll elements extend from the opposite sides of the end plate. The dual scroll structure causes the axial forces acting on the end plate of the orbiting scroll from the compressed fluid pressure to be substantially reduced or balanced. Hence, the need for a thrust bearing to support the orbiting scroll is eliminated and so is the corresponding friction wear and power loss.
However, in the prior art, the orbiting scroll, no matter whether it is centrally driven or peripherally driven, makes orbiting motion with a fixed orbiting radius. U.S. Pat. No. 4,192,152 to Allen E. Armstrong et al. discloses a radial compliant linking means to accommodate the thermal expansion differences between the scroll members and frame of the housing. This so-called xe2x80x9cradial compliantxe2x80x9d linking means is not a true radial compliant mechanism in the sense of being typically and commonly accepted in the industry. A typical xe2x80x9cradial compliant mechanismxe2x80x9d refers to a mechanism that can provide the orbiting scroll with freedom to travel radially until flank-flank contact between the orbiting scroll and the fixed scroll takes place to seal off the compression or expansion pocket. When incompressible fluid is trapped in the compression pocket or debris is involved between the scrolls, the orbiting scroll can yield radially backwards from the fixed scroll to accommodate the situation.
U.S. Pat. No. 3,817,664 discloses a pivot shaft and coupling means, i.e. a mechanical radial compliant mechanism, where the orbiting scroll is compliant radially through a coupling mechanism driven by a pivot shaft, which in turn is urged by a mechanical spring. This patent also discloses an axial compliant mechanism where the orbiting scrolls are urged towards the fixed scroll to achieve tip-base contact between scrolls by the pressure of the discharge fluid for better radial sealing. This radial compliant mechanism is not practical due to the pivotal shaft and is not convenient for high rotation speed, such as a couple of thousand RPM (revolutions per minute) or higher.
In oil-free and large horsepower applications, due to the severe working conditions for the former and heavy load for the later, both call for stronger anti-rotation and coupling mechanisms than an Oldham ring mechanism, which is currently widely used in air conditioning and oil flooded scroll applications. The peripheral crank handles, as taught in U.S. Pat. No. 3,802,809, provide a strong and reliable anti-rotation and coupling mechanism. However, it restricts the orbiting scroll from radial compliance, thus sacrificing the tangential sealing between the fluid pockets formed between orbiting and fixed scrolls.
To overcome the shortcomings of conventional scroll-type fluid displacement apparatus, the present invention provides a xe2x80x9cfloating scrollxe2x80x9d mechanism for scroll type fluid displacement apparatus. The dual orbiting scroll has spiral vanes on both sides of the end plate. In a floating scroll, the orbiting scroll is dynamically well balanced, axially and radially. The scrolls are fully or semi-axially and radially compliant for maintaining minimum contacting forces between components, hence achieving good sealing for high speed, high efficiency, low friction wear and power loss. A crank shaft-sliding knuckle and/or peripheral crank handles-sliding knuckle mechanism provide the dual orbiting scroll with radial compliant capability. A synchronizer is used to synchronize the orientation of the crank handles to prevent the mechanism from jamming during operation and start up. The scroll can be single stage or multi-stage, depending on the compression ratio, working media and other factors of the applications.
An object of the invention is to provide an improved scroll-type positive fluid displacement apparatus, which uses peripheral multiple crank handles to assure the circular translation, i.e. orbiting motion, of the orbiting scroll relative to the fixed scroll. At the same time, the scroll-type apparatus provides the orbiting scroll with the freedom to adjust its orbiting radius compliant to the fixed scroll spiral element by synchronizing the peripheral crank handles to eliminate possible mechanical jam of the handles.
It is another object of this invention to provide an improved scroll-type apparatus in which the orbiting scroll has spiral elements extending from the opposite sides of the end plate, a so called xe2x80x9cDual Orbiting Scrollxe2x80x9d. Both sides of the dual orbiting scroll are dynamically similar or identical, i.e. the axial forces acting on both sides of the dual orbiting scroll are balanced or its difference is minimized. An axial compliant mechanism, by pressurizing a plenum, urges one scroll member towards the other scroll member with a controlled axial force that is just enough to overcome the opposite forces to maintain very light tip-base contact and thus, to achieve the radial sealing. The orbiting scroll with axial and radial compliant mechanisms is xe2x80x9cfloatingxe2x80x9d in the sense of force balance. The floating scroll technology allows the scroll apparatus to operate at higher rotating speeds to achieve higher fluid displacement capacity with a relatively small size and weight of the apparatus. This results in a reduced friction, reduced wear, highly efficient, compact and light scroll-type fluid displacement apparatus.
Other objects of the invention will in part be obvious and will in part be apparent hereinafter.